1. Field of Invention
The invention relates to a method for determining the network topology of a bus system having a number of bus subscribers, which are arranged on mutually connected bus segments of a bus line. It also relates to an apparatus for carrying out the method.
2. Description of the Related Art
A bus system or field bus within a complex network having a number of bus segments has a large number of bus subscribers in the form of field appliances, such as sensors, actuators, programmable logic controllers and control stations. By way of example, the so-called PROFIBUS DP network normally has up to 127 bus subscribers, to which subscriber addresses from 0 to 126 may be allocated. In this case, up to 32 network components can be connected as bus subscribers to one bus segment, as a section of a bus line.
The line length of an individual bus segment is limited, depending on the so-called baud rate. This indicates the data rate which can be transmitted over that bus segment. With a normal data rate of 12 M baud=12·106 bits/s, it follows that one bit is equal to a length of 83 ns. Within the network, the individual bus segments are connected by line drivers or so-called repeaters, which are used to provide branches in the field bus or network. In this case, the network topology of the bus system should be known, and is governed by the arrangement, that is to say by the sequence and the relative distance between the bus subscribers on the individual bus segments (bus segment topology), and by the connection of the bus segments to one another.